1. Field of the Invention
The present invention relates generally to heat exchangers, and more specifically to refrigerant tubes for a heat exchanger.
2. Disclosure Information
FIGS. 1-2 illustrate the typical construction of most heat exchanger refrigerant tubes according to the prior art. As typified in FIG. 2, this construction includes a flat metallic tube 10 having flat upper and lower walls 12/14 with a plurality of reinforcing walls 16 connected between the upper and lower walls. These reinforcing walls 16 extend parallel to each other along the length of the tube 10, thereby forming a plurality of parallel flow channels 17 each bounded by the upper and lower walls 12/14 and two reinforcing walls 16. This tube construction can be made using a variety of approaches, such as those disclosed in U.S. Pat. No. 5,638,897 to Hirano et al., U.S. Pat. No. 5,784,776 to Saito et al., and U.S. Pat. No. 5,799,727 to Liu (each of which being incorporated herein by reference).
Such refrigerant tubes can be generally grouped into two categories: discrete flow and non-discrete flow. Discrete flow refrigerant tubes have parallel flow channels 17 which do not communicate with one another along the length of the tube; as illustrated in FIG. 3A, the reinforcing walls 16 of discrete flow tubes completely segregate each flow channel 17 from its neighboring flow channels. Non-discrete flow tubes, on the other hand, provide a plurality of apertures or openings 18 in the reinforcing walls 16, as illustrated in FIG. 3B; these openings 18 permit fluid communication among adjacent flow channels 17. Non-discrete flow tubes are more difficult to manufacture, but have the advantage of providing better heat transfer because of the cross-flow of refrigerant fluid among the flow channels through the openings 18.
Although it is known to provide such openings 18 to facilitate fluid cross-flow, no guidance has heretofore been provided for designing the size and spacing of these openings so as to optimize the heat transfer potential of non-discrete flow refrigerant tubes.